Passive "help me to know the reason"

[M!do]

Good evening teachers,

Please, I would like to know why this sentence is in this form. On skype when I declined a call, it was said, "Call from viviana declined."

Is this a passive statement?

I know if that was a passive, it could be "Call from viviana was declined."

thanks in advance

[5jj]

Yes, it's passive. It could be "The call from viviana was (or has been) declined"

[M!do]

but why they didn't say it completely?

[5jj]

Because notices, signs, messages, etc want to convey the intended meaning as concisely as possible.